This invention relates generally to a terminal block and motor protector holder assembly for a hermetic compressor of a refrigeration system. More particularly, the invention relates to a combined terminal block and motor protection holder for a hermetic compressor which is mounted inside the compressor casing.
Hermetic compressors are well known in the prior art and generally comprise a casing, a motor mounted inside the casing and a compressor unit which is driven by the motor. In high side hermetic compressors the compressed refrigerant is discharged from the compressor unit into the casing and then flows over the motor windings to cool the same. The compressed refrigerant then flows through a discharge tube out of the compressor casing and into a condenser for cooling of the compressed refrigerant. It is imperative, for the proper operation and protection of a hermetic compressor, that the temperatures of the motor windings not exceed a predetermined temperature level. Since the compressed refrigerant is used to cool the motor windings, the temperature of the refrigerant, after flowing over the motor windings, gives an indication of the temperature of the motor windings. Thus, it is important to monitor the temperature of the compressed refrigerant after it flows over the motor windings and to shut down the compressor if the temperature of the refrigerant exceeds a certain predetermined level. In a hermetic compressor, electrical connections to the compressor motor from a supply of electric energy must also be made. These conductors must be routed through the wall of the compressor casing to connect the motor windings to an external supply of electric energy.
Prior art hermetic compressors have provided various systems for connecting the supply of electric energy to the motor windings and for protecting the motor windings from excessive heating. Conventionally, a terminal assembly is welded to the compressor casing and a temperature sensitive motor protector is mounted on a mounting bracket inside the casing. The power supply is connected to the terminal assembly and leads are then used to connect the terminal assembly to the motor windings and to the motor protector. Thus, these prior art systems have used relatively complex and costly electrical interconnection and protector systems. Generally, a total of six (6) leads must be used for making the interconnections in such prior art systems. It is therefore desired to reduce the number of parts for providing the internal electrical connections in a hermetic compressor, to provide a convenient motor protector holder to improve the reliability of the compressor and to reduce the cost of the compressor.
Another problem with prior art compressor motor protection systems has been that, in some situations, the protectors have been responsive to rapid fluctuations in the temperature of the compressed refrigerant, which fluctuations were not indicative of an overall excessive temperature condition. In still other prior art motor protection systems, the motor protector has been too unresponsive to temperature variations as the protector was not located in a position wherein it sensed the average temperature of the discharged compressed refrigerant and therefore gave an incorrect indication of the temperature of the motor windings.
In one prior art connector block and protector holder assembly, the motor protector is located on the outside of the terminal block and the entire terminal block and protector assembly is connected to the terminal pin assembly which is located on the inside wall of the compressor casing. However, since in this prior art structure, the terminal block and protector assembly is not located in the vicinity of the inlet to the compressor discharge tube for discharging compressed refrigerant from the compressor, the protector was not sensitive to the average temperature of the compressed refrigerant. Furthermore, by mounting the protector on the outside of the terminal block housing, the protector was likely to give an incorrect indication of the temperature of the compressed refrigerant as the protector was likely to indicate the temperature of spikes of hot refrigerant rather than the average temperature of the compressed refrigerant. It is therefore desired to provide a combined terminal block and overload protector holder assembly for a hermetic compressor wherein the overload protector is insulated or shielded from direct contact with hot spikes of compressed refrigerant. It is furthermore desired to provide such an assembly wherein the number of electrical connectors and leads is reduced to a minimum thereby improving the reliability and reducing the cost of a hermetic compressor.